in the eigenfrequency solver sequence (quite deep down in the solver tree), you have the option for the normalisation of the eigenvectors/frequencies, such as RMS, and model mass, once changed you need to rerun your solver, then your mass participation factors (in kg but units are not mentioned) are the SQUARE of the model participation factors (see the Structural doc)

I have the participation factors (u,v,w) for a particular mode. I want to calculate the effective or modal mass for that mode. Really confused about that. Is it mass participation factor or modal participaton factor?

After running my simulation and computing the effective masses for each direction, let's call them m_eff_x, m_eff_y, m_eff_z, I would like to combine them in order to obtain a meaningful effective mass for each mode i (something like sum over all directions instead of sum over all modes -> m_eff_i = function(m_eff_x_i, m_eff_y_i, m_eff_z_i) ).

normally the effective mass variable are normalised such that the sum of the square of each participative mass value, per direction adds up to the total mass of the object, so what I often do is to normalise mode_mass_x^2 / Total_Mass and check that I select sufficient modes to get 70-80% or more of the total mass per direction